The present invention pertains to an electrical control module, and, in particular, to a module adapted for use within a Power line Control Component ("PCC") to enhance electrical appliance control.
The control of electronic devices within a particular location previously has been achieved via a data communication system that works over the power lines of that location. Existing power line control systems typically utilize a centrally located transmitter connected to the power line, as well as receivers connected to the power line and circuited with electrical appliances. The receivers, upon the receipt of certain commands from the transmitter, operate to control the electrical appliances and thereby achieve a remote control of such appliances from the site of the transmitter. The transmitter and receivers communicate over the interconnecting power lines, such as via the X-10 protocol developed by Pico Electronics of Fife, Scotland. A further description of the X-10 protocol and PCCs are found in U.S. Pat. Nos. 4,200,862 and 5,491,463, which both are in their entirety incorporated herein by reference, the latter patent is assigned to the assignee of the present invention. While useful, existing power line control systems suffer from a variety of shortcomings which limit their desirability from a practical standpoint, as well as may make their implementation prohibitively expensive in certain circumstances.
One problem with existing power line control systems is that current Application Specific Integrated Circuits ("ASIC") solutions for PCCs have limited end device applications as they are made to operate with specific hardware devices. In particular, to support a new end device, a new ASIC chip to perform the required task must be custom manufactured. This technique frequently is so expensive as to make many applications commercially impractical.
Another problem with existing power line control systems relates to the lack of good signal to noise response and sensitivity. Most current X-10 based products utilize band pass filters, Automatic Gain Control ("AGC") and frequency counting methods to determine the presence of a signal on the power line. While the X-10 AGC is helpful when there is noise on the line, as typically implemented it is only useful if the signal is about twice as large as the noise on the line. Consequently, weaker signals might not be picked up on some occasions, and the commands being relayed via those weaker signals go unexecuted.
Another problem with the existing power line control systems is the accuracy of the transmit carrier frequency and signal amplitude. Most X-10 based transmitters utilize a slug tuned LC oscillator which can vary from 118 to 122 kHz. Receiver sensitivity is reduced when the received carrier frequency is not 120 kHz. The carrier amplitude of X-10 based transmitters can also vary from 2 to 3.5 Vp-p into a 5 ohm reactance loaded power line. Communication reliability is reduced when the transmit carrier amplitude is reduced.
Still another problem is that new product development is time consuming and therefore slow. Current practices require re-layout and design of common circuitry for new products, and this process lengthens the time to market for new PCCs. Moreover, the need to rewrite the microprocessor code for common communications routines into each new product is time-consuming.
Another problem is that existing PCCs are inflexible for users to set protocol options. Current products are coded in permanent non-volatile memory to handle a fixed protocol and therefore there is no capability for options to be adjusted according to the preferences of the end user for system enhancement.
Another problem with most power line control systems is that because acknowledgment by receivers of messages from the transmitter is absent, it is not possible to ensure that messages are received and acted upon. Consequently, systems that are dependent on getting a signal to an end device need to send the messages multiple times to try and ensure that the message does indeed reach the receiver. This multiple transmission requirement reduces the overall band width of the system and increases the likelihood that other signals will not have a chance to reach their destinations.
Another problem with existing power line control systems results from large instruction sets being run from a central controller. Specifically, end devices are set to respond to a particular address, which may be part of a group depending on the command needed to be implemented. The group address is set with a hardware switch, and as a result individual devices can not respond to commands that are not directed to their group. This shortcoming is problematic when the user desires to send the same command to a set of devices that belong to different groups, as the central controller typically handles this task by sending the required commands to each of the devices in the set. In most cases, this requires a large series of commands being sent to enable and operate the individual devices, which undesirably increases traffic and noise on the power line and reduces bandwidth and response time.
Still another shortcoming with power line control systems is the inability to implement new commands. Current devices have no easy means to add new commands. Moreover, a PCC's protocol/application settings cannot be read/updated while the PCC is installed in a power line control system, and typically the PCC must be disassembled to allow for setting changes.
Still another shortcoming is that many current X-10 based systems only handle the standard code command set (0-255 possible addresses). With such systems, not enough addresses may be available in some situations, such as when being used in a large hotel.
Thus, it would be desirable to provide a device which may be used to overcome these and other shortcomings of the prior art.